The adage that you can’t manage what you don’t measure holds especially true for water, whether you’re referring to a portfolio of existing buildings or are in the planning stages of a new building
By Daniel Hartsig
Existing buildings: Our most significant opportunities for water conservation are in existing buildings, which represent about 98 percent of the US building stock at any given time according to 2012 CBECS data.
When our clients started requesting water scores, we took on the challenge of benchmarking a fluid portfolio of 400 buildings we manage for others. We identified five critical steps needed to conduct effective comparisons: metering, mentoring, monitoring, metrics, and management.
Receiving building level water usage was the first hurdle. Many buildings had meters owned by others hesitant to report usage. Some buildings needed meters installed or replaced, others simply weren’t accessible. Inaccurate or inconsistent data slowed us down. Mislabeled meters and obscure water distribution frustrated our efforts and different scales and units used on some meters added confusion.
To keep an eye on the numbers we used a tool that our operators were already working with: the EPA’s ENERGY STAR® Portfolio Manager. Weekly meter readings were the best balance of accuracy and implementation costs, and submetering large uses was needed to set our metrics.
Building size, type, occupancy, climate zone, and the presence or absence of cooling towers or irrigation was used to establish water use intensities (WUI’s) and produce our scores. Now in our third year, we’ve used these scores to implement our corporate water reduction goals.
New development: Each year, new construction only adds 2 percent to the building stock, so significant change is limited, but conservation efforts are easier. Water savings strategies shift from benchmarking and management to collaboration and efficiency.
One tool works consistently to drive the biggest reductions—studying the site’s water balance.
A good water balance identifies all potential inputs, uses, and outputs, highlighting cost effective sourcing and reduction strategies. Owners are often surprised by the number of disciplines that should be involved.
You’ll want to quantify supply and waste for domestic, mechanical and process systems; identify graywater sources in foundation dewatering, condensate, reject water and rainwater as well as evaporation losses; research municipal and ground water sources; limits on water leaving the site; opportunities to use native plants instead of irrigating; and understand the forms of water treatment that may be needed to expand supply and reuse options.
A water reduction charrette early in the design process should include plumbing, mechanical, process, utility, civil, landscaping and water treatment designers.
Local concerns: Increased withdrawal and contamination upstream, as well as a project’s effects on downstream users are risks of any project.
A good risk assessment looks at potential complications with supply as well as effects on downstream users. These factors can modify long term operating costs, potentially accelerating return on investment calculations.
When looking for ways to reduce water impact, the building’s power supply cannot be ignored. Energy use requires water for the extraction and refinement of fuel, the production of power (steam turbines) and the rejection of heat. Water consumption requires energy for supply, treatment (potable and wastewater), and heating.
According to the DOE’s Water-Energy Nexus report of 2014 and the CBECS median electrical energy usage for offices, the average US office building uses 75 of fresh water, per square-foot per year, attributed solely to electrical consumption. It goes up to 300 if you account for thermal pollution. The EPA median water usage for offices is only 10 gallons/square foot/year.
This means that in most areas of the U.S., cutting electrical use can result in greater water savings than cutting direct water consumption by the same percentage.
Regional impacts: The construction and operations of a building consumes goods, each of which has their own water consumption and impact on local watersheds.
Similar to a life cycle assessment, a true water footprint incorporates the water usage impacts of the primary products and materials consumed by the building, over the life of the building. This can be an incredibly difficult process, but the Alliance for Water Stewardship has developed a standard that can guide you through this process.
Few companies go this far, but for those that do, their water footprint can set solid monetization metrics and mitigate their water risks, informing cost effective methods to achieve long term water conservation goals.
The trouble is not that water is consumed or destroyed, but that in using it we often make it unusable or inaccessible to ourselves and others. When we all use less, we gain resiliency to shock and the freedom to adapt.
Daniel Hartsig is the Manager for New Construction Services at Transwestern. He may be reached at Daniel.Hartsig@transwestern.com.